WASHINGTON (CNN) – Top Obama aides Larry Summers and David Axelrod heard a barrage of criticism late Thursday about the stimulus plan at a closed-door meeting for all Democratic senators, according to several participants who spoke afterwards.

Sen. Tom Harkin of Iowa said he was “concerned about the way Mr. Summers and others are going on this.” In particular, he dismissed the tax breaks for individuals as a return to “trickle down” economics that won’t work.

Harkin said the Obama aides were “non-committal” about whether they would change their plan.

In a Florida press conference, Martinez said his decision was not based on the likelihood he would face a tough reelection fight.

"I've faced much tougher obstacles in my life," he said. "My decision is not based on re-election prospects, but on what on what I want to do with the next eight years of my life."

The first term senator and onetime National Republican Committee chairman narrowly won his first Senate race in 2004. Martinez also served as Secretary of Housing and Urban Development during President Bush's term.

One congressional source cited Martinez's age, 62, and said "he is ready for the next chapter in his life."

Instead, Senate Democrats will likely strip Lieberman of his chairmanship of an environmental subcommittee - a considerably less prominent position than his homeland security post.

That outcome would be at odds with Senate Majority Leader Harry Reid's initial intentions. Sources told CNN last week that Reid had informed Lieberman it was likely he would lose his chairmanship of the committee and instead assume a leadership post on a less prominent panel. Lieberman told
Reid that offer was "not acceptable," according to sources.

The Democratic caucus will formally meet Tuesday morning to hold a secret ballot vote on Lieberman's future, but the sources suggested the outcome of that vote may already be a foregone conclusion.